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Crystal structure of E. coli RecE exonuclease reveals a toroidal tetramer and a conserved architecture for processive DNA digestion.
Author(s) -
Zhang Jinjin,
Xing Xu,
Herr Andrew B.,
Bell Charles E.
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.655.5
Subject(s) - tetramer , exonuclease , dna , biophysics , replication protein a , d loop , nuclease , dna clamp , homologous recombination , chemistry , biology , dna polymerase , biochemistry , gene , dna binding protein , rna , enzyme , reverse transcriptase , transcription factor , mitochondrial dna
The E. coli RecET recombination system is a classic model for understanding the repair of double strand DNA breaks by the single strand annealing pathway. RecE protein, one of the two key components of this system, is a processive ATP‐independent exonuclease that specifically binds to double strand DNA ends and degrades the 5′‐terminated strand. The 3′‐ended ssDNA tail that is generated serves as a substrate for RecT recombinase, the other key component of RecET system, which promotes homologous recombination. In this study, a 2.8 Åresolution crystal structure of the C‐terminal nuclease domain of RecE, residues 606 ‐ 866, was determined. RecE forms a toroidal tetramer with a central channel that is wide enough to bind double strand DNA at one end, but is partially plugged at the other end by the C‐terminal segment of the protein. Four narrow tunnels, one within each subunit of the tetramer, lead from the central channel to the four active sites, which lie about 15 Åfrom the channel. The structure suggests a mechanism in which DNA binds to the open end of the central channel, the 5′‐ended strand passes through a tunnel to access and be degraded by one of the four active sites, and the 3′‐ended strand passes through the plugged end of the channel at the back of the tetramer.